After you have logged in, click "Billing" (shown below) and you will be taken to your billing information where you can update your billing address, pay online, update credit card information and more.

This is inaccurate. These instructions don't work. Also, users should be careful. This system automatically saves any card you enter, does not request permission to save card info, and also automatically creates an automatically recurring payment for the last card you used without the permission of the cardholder. One-time payments are not possible in this system, and there are no warnings. Also, the card information update feature as above is false, and has been that way for a very long time, and the company is already aware of it, so it's likely intentional. Just so everyone knows ahead of time. Hopefully, this helps.